Where an engine and transmission are mounted transversely with a differential as a power train in a motor vehicle to drive either the front or rear wheels, it is common practice to employ a torque strut between the engine and the vehicle chassis to control pitching of the power train. Normally, elastomeric bushings are used at the pivot connections of the torque strut that are configured so as to provide a soft substantially linear spring rate at small vibratory pitching amplitudes occurring with low torque. In addition, the bushings may be configured so that for large pitching power train amplitudes occurring at high torque, the strut mounts then additionally provide non-linear rates that increase with increasing large pitching amplitudes so as to best isolate such pitching vibrations of the power train. An example of such a torque strut arrangement is disclosed in U.S. Pat. No. 4,240,517 assigned to the assignee of this invention. In such prior art struts, the spring rates are built in or fixed and are a compromise found to be best suited to the full range of pitching motions to be encountered. And thus such struts are not ideally suited to controlling all the power train pitching motions as the engine speed and torque vary through wide ranges.